1. Field of the Invention
The present invention relates to a data storing apparatus, a method thereof, a data delivering apparatus, and a method thereof suitable for storing and reproducing a large amount of video data and audio data corresponding thereto used in for example a broadcasting station.
2. Description of the Related Art
In a broadcasting station, video data and audio data of a commercial message, a drama, and so forth are handled as a pair. On the other hand, for a news material used in a news program, audio data is added to video data that has been prepared. Thus, in this case, audio data and video data are often separately handled. When video data and audio data are handled as a pair, no problem takes place. However, when they are separately handled, some processes are required for them.
Conventionally, video data and audio data are simultaneously recorded on a linear record medium such as a magnetic tape. Thus, with one record medium, it is impossible to simultaneously reproduce video data recorded in a particular area and audio data recorded in another area. To simultaneously reproduce them, it is necessary to use for example two video cassette recorders (hereinafter, referred to as VCRs) so as to reproduce video data with one VCR and reproduce audio data with the other VCR.
In contrast, new type record mediums such as a hard disk drive and a magneto-optical disc drive (referred to as HDD and MO, respectively), nonlinear data is randomly accessed. Hereinafter, such record mediums are referred to as nonlinear record mediums against the linear record mediums such as a magnetic tape. When a video signal and an audio signal are digitized and recorded as video data and audio data on a nonlinear record medium, the video data and audio data can be separately reproduced in some measure.
In recent years, as the CATV (Cable Television) and digital broadcasts are becoming common, a large number of information channels are being provided. Thus, there are needs for recording and reproducing a plurality of channels of video/audio data with one video/audio data recording and reproducing apparatus and for reproducing one channel of video/audio data while recording another channel therewith. To satisfy such needs, an apparatus referred to as video server (A/V server (Audio and/or Video) server) that records video/audio data with a random access record medium such as a hard disk is becoming common.
Generally, in a broadcasting station and so forth, video data should be reproduced with high quality. Thus, an A/V server used in a broadcasting station and so forth should have high data transmission rate for high picture quality and high audio quality and a large storage capacity for long time data.
Thus, a recording and reproducing apparatus that stores video data and audio data and processes them in parallel with a plurality of hard disk drives (HDDs) is used as an A/V server. With such an A/V server, an attempt for accomplishing a high speed data transmission and a large storage capacity has been made. In addition, an attempt for accomplishing a high reliability structure with parity data that allows the system to operate even if one HDD gets defective has been made.
Thus, a variety of applications become available. For example, an A/V server having multiple channels can be accomplished. In other words, for example, multiple channels of programs corresponding to contents and broadcast type can be accomplished. For example, material data composed of a plurality of programs of video/audio data may be distributively recorded and they are delivered at the same time. Alternatively, the same material data may be delivered on a plurality of channels so that the program start time differs in each of the channels. With such an A/V server, a VOD (Video On Demand) system and an NVOD (Near Video On Demand) system that deliver many channels of video data in parallel can be accomplished.
Such an A/V server can be applied to a recording and reproducing apparatus corresponding to RAID technologies using a plurality of sets of HDDs. The RAID technologies were proposed by Patterson et. al., in (“A Case for Redundant Arrays of Inexpensive Disks (RAID)”, ACM SIGMOND Conference, Chicago, ILL, Jun. 1–3, 1988).
In the paper by Patterson et. al., RAID systems are categorized as RAID-1 to RAID-5 corresponding to the redundancies and structures thereof. In RAID-1, a mirroring structure of which the same data is written to two HDDs is used. In RAID-3, input data is divided into data blocks having a predetermined data length and the divided data blocks are recorded to a plurality of HDDs. In addition, parity data is generated by exclusively ORing the data blocks recorded in the individual HDDs and writing the parity data to another HDD. In RAID-5, data is divided into large data blocks. One divided data block is written to one HDD. In addition, data blocks corresponding to individual HDDs are exclusively ORed. The resultant data (parity data) is distributively recorded to other HDDs.
Conventionally, video data and audio data are recorded to a RAID type recording and reproducing apparatus. Video data for a predetermined time unit (for example, one frame) and audio data corresponding thereto are recorded on adjacent positions of a record medium (HDD) as shown in FIG. 1. Referring to FIG. 1, video data 101 and audio data 102 are recorded from the outer periphery to the inner periphery as circumferential tracks on a hard disk 100 frame by frame.
However, in this method, when video data and audio data are reproduced in a combination, a seek time takes place. In other words, since the data amount of video information is large, the seek time of the HDD cannot be ignored against a required data transmission rate.
To solve the problem of the seek time, a method for recording video data and audio data to different HDDs has been proposed. FIG. 2 shows an example of the structure of a conventional A/V server. An input device 121 that is composed of for example a digital VCR and a satellite receiving system is connected to an A/V server 120. The input device 121 supplies digital video data and audio data to the A/V server 120. In addition, an output device 122 composed of for example a monitor and a transmitting system is connected to the A/V server 120.
The A/V server 120 has an HDD array 124 and a HDD array 125. The HDD array 124 and the HDD array 125 record video data and audio data, respectively. The inputting process of the input device 121, the recording processes of the HDD arrays 124 and 125 for the input data, and the outputting process of the output device for the reproduced data are controlled by a processor 123.
Video data and audio data are extracted from the input data received from the input device 121. The extracted video data is recorded to the HDD array 124 under the control of the processor 123. On the other hand, the extracted audio data is recorded to the HDD array 125.
According to such a method, video data and audio data are separately recorded to the HDD arrays 124 and 125, respectively. Thus, video data and audio data extracted from the HDD arrays 124 and 125 can be freely combined and used. However, in this method, the HDDs arrays 124 and 124 that record video data and audio data, respectively, are required.
In such a method, when one of the HDD arrays 124 and 125 becomes full, even if the other is not full, no further data can be recorded.